This is a 371 of PCT/FR00/02274, filed Aug. 8, 2000.
The invention relates to apparatus for non-destructive extensometric measurement of the support forces that can be exerted by an orthesis of the elastic hose type (where said forces are more exactly both supportive and compressive), the term xe2x80x9celastic hosexe2x80x9d being understood broadly, including various kinds of hose such as short socks, socks, thigh-high stockings, self-supporting stockings, tights, maternity tights, men""s tights, or half-tights.
The term xe2x80x9cextensometric measurementxe2x80x9d is used to mean measurement that consists in applying deformation to a precise location of the hose and in measuring the force applied locally by the hose under the effect of said deformation, which force is a function of the elastic characteristics of the materials used and of the structure of the article.
It is necessary to be able accurately and reproducibly to measure the force which a given compressive orthesis can apply, in particular in order to verify that it complies with nominal values specified as a function of a selected class of support.
Such measurement is important particularly during manufacture, in order to verify articles as they come off the knitting machine while performing quality control and optionally adjusting the knitting machine.
Nevertheless, this application is not limiting, and the invention can be used for numerous other purposes, e.g. for testing new materials, developing new products, investigating product fatigue, etc.
Various extensometric measurement apparatuses and protocols have already been proposed for these purposes. However, such methods and apparatuses all present one or more of the following drawbacks:
they are destructive, in particular in systems that use traction claws for imparting forced deformation to the hose;
inspection times are very long: some measurement protocols can take as long as 48 hours, which is incompatible with industrial constraints of the manufacturing quality control type;
the number of measurement points is small, even though the uniformity of hose makes it important to obtain as large as possible a number of measurement points over the entire length of an article;
the equipment is expensive; and
multiple jigs need to be provided as a function of the size of the hose or as a function of different hosiery articles, thus requiring a large amount of manipulation.
The object of the present invention is to mitigate all of the above drawbacks by proposing a non-destructive extensometric measurement apparatus that is suitable (amongst other things) for production quality control, because of its robustness, the speed with which it can be used, and its flexibility, including the option of adapting quickly and simply to articles that are different or to different sizes of the same article.
The apparatus of the invention also presents the following advantages:
accurate measurement;
reliable measurement making it possible to provide data reproducibly and independently of the skill of an operator;
measurement that is performed simultaneously at a large number of points;
implementation can be simple and quick;
the data obtained can be digitized, stored, processed, and displayed, in particular for interfacing with computer processing; and
it can be used to inspect all of the standard sizes, executions, and lengths currently in production, and also all of the articles that are made to measure.
To this end, the extensometric apparatus of the invention is characterized in that it comprises: a jig suitable for receiving an orthesis engaged thereon, said jig having two elongate branches; expander means cooperating with facing ends of the branches to move them apart from each other transversely to their long dimension; control means for controlling the expander means and suitable for moving the branches so that they move apart from each other progressively and in controlled manner; and sensors distributed along the length of at least one of the branches and suitable for measuring the force applied locally to the branch by the orthesis at the locations of the respective sensors in terms of a component perpendicular to the profile of the branch.
According to various advantageous subsidiary characteristics:
the branches are pivotally united at their ends remote from their ends which co-operate with the expander means, the movement of mutually moving apart from each other being a pivoting movement about the corresponding pivot point;
the sensors include as sensor elements in contact with the orthesis buttons that lie flush with the outside profile of the branch in which they are located;
the expander means comprise a rectilinear branch carrying the sensors and a curvilinear branch whose profile corresponds to that of a leg suitable for receiving the orthesis;
the apparatus includes means for determining the transverse elongation of the orthesis at the location of each of the sensors as a function of the spacing imposed on the branches by the expander means;
the apparatus includes means for recording a plurality of pairs of measurements for each sensor, each pair comprising a force measurement and an elongation measurement, in particular, with means for dynamically determining a force/elongation characteristic; and
the apparatus includes means for dynamically determining a force/elongation characteristic.